The Caribou (also more commonly known as Reindeer) in North America is a deer from the
Arctic and Subarctic. While being overall widespread and numerous some of it's subspecies are rare and some completely extinct.
The Caribou varies quite a bit in colour and size, both male and female have antlers, though these tend to be larger on males and there are a few populations where the females don't have them at all.
As mentioned already the colour of their coats vary considerably in both male and female but also depending on the season and subspecies. Northern Caribou are smaller and whiter than the Southern Caribou which are larger and have a darker coat.
Since 1961, Caribou have been divided into two major groups, the tundra Caribou with six subspecies and the woodland Caribou with three subspecies.
Caribou have specialized noses featuring nasal turbinate bones that dramatically increase the surface area within the nostrils. Incoming cold air is warmed by the animal's body heat before entering the lungs, and water is condensed from the expired air and captured before the deer's breath is exhaled, used to moisten dry incoming air and possibly absorbed into the blood through the mucous membranes.
The Caribou's hooves adapt to the season - in summer when the tundra is soft and wet, the footpads become sponge like and provide extra traction. In winter, the pads shrink and tighten - exposing the rim of the hoof, which helps cut through ice and crusted snow keeping it from slipping. This also enables them to dig through the snow to their favourite food, lichen.
Caribou have a variety of predators that prey heavily on them. Golden Eagles take young calves and are the most prolific hunter on calving grounds. Other larger predators consist of Brown bears, wolves and on the rare occasion when they encounter one another, Polar bears.
Some populations of the North American Caribou migrate the furthest of any terrestrial mammal, travelling up to 3,100 miles a year, and covering 390,000 sq miles.